Does my concept for light speed travel pass the “handwave test”?

Basically my idea for a light speed travel concept (not faster than light) is the Zero Mass Field. I am aware that as far as we know this is impossible, but want to know if this makes logical sense and is believable as a fictional concept. My understanding is that anything with mass can't reach the speed of light because to do so would require infinite energy. I also believe anything with zero mass (e.g photons, gluons) HAVE to be moving at light speed.

So my concept is the Zero Mass Field - a spaceship starts sublight travel in the desired direction before activating the field generator which creates a zero mass field making everything in it zero mass and speeds towards the interstellar target at the speed of light. The passengers and ship itself would perceive an instant arrival at the destination due to relativity.

How you know when to stop is for another question.

(I used the ftl tag as there doesn't seem to be an "exactly light speed" tag)

• Really good question! Frankly, I'd have a harder time accepting the notion that "light speed travel" does not actually imply moving faster than c. It's a fairly standard SciFi trope that "light speed" is equivalent to FTL (faster than light(speed)) travel. – elemtilas Dec 10 '20 at 19:32
• If the ship is traveling at the exactly the speed of light, how your ship's computer turns zero mass field off, since time on the ship would stand still? – Darth Biomech Dec 10 '20 at 20:11
• @DarthBiomech providing the answers here allow me to proceed with my light speed drive in some form this is already planned as my next question, and is actually the thought that lead me to asking this first. – Wiggo the Wookie Dec 10 '20 at 21:19
• What's the big advantage to this over something like a Bussard ramjet that simply approaches the speed of light? This seems like the equivalent of building a Concord as opposed to a 747. Sonic booms were enough to stop the Concord from being used apart from the Atlantic ocean, but this would potentially set off something worse than a nuclear explosion if it fails(and as Zeiss Ikon notes, this is almost certain). – Adam Reynolds Dec 10 '20 at 21:55
• There's an Isaac Asimov short story The Billiard Ball involving a similar device on a much smaller scale – Pete Baughman Dec 11 '20 at 5:15

It is more than good enough for science fiction. This is actually what the Mass Effect is all about in the videogame series that bears that name:

Mass effect fields are created through the use of element zero. Element zero can increase or decrease the mass content of space-time when subjected to an electrical current via dark energy. With a positive current, mass is increased. With a negative current, mass is decreased. The stronger the current, the greater the magnitude of the dark energy mass effect.

In space, low-mass fields allow FTL travel and inexpensive surface-to-orbit transit.

It is interesting that you are limiting your version to actual light speed (and nothing else). If you went any faster, you'd be fined by the Auditors of Reality for breaking causality :)

• That was my first thought as well. There's still some handwaving as to how you can decrease mass to 0 and not have every atom / electron fly away, but for a story mechanic it's a good enough light-speed. – abestrange Dec 10 '20 at 19:45
• @abestrange molecules in objects and bodies are kept together due mostly to the electromagnetic force, not due to gravity ;) – The Square-Cube Law Dec 10 '20 at 19:47
• Do the strong/weak nuclear forces require mass? – StephenS Dec 10 '20 at 19:55
• @StephenS not that I'm aware of. Only gravity works on mass. – The Square-Cube Law Dec 10 '20 at 19:58
• @abestrange perhaps the handwave could involve the idea that while at light speed the atoms and electrons do not experience time, and the switch to zero mass and light speed is instantaneous. As I said in the question how you get out of this state "while" you are not experiencing time will probably be my next question! – Wiggo the Wookie Dec 10 '20 at 20:44

Here's how the first complete test would go (all the prototypes exploded violently, but it was hypothesized that was due to running the generator too deep in a gravity well).

Test drone is launched by conventional rocket, and uses gravity assists from Earth, Venus, Earth, and Venus again to get to the orbit of Saturn in only seven years. All systems have passed multiple tests en route, so as soon as the Sun's space curvature is low enough (for the theorists), the unit is powered up.

Because it's a much larger generator than the prototypes tested on Earth, the explosion is bright enough to see with the naked eye from Earth.

The problem you have is that every particle in an object has its own particular velocity, and for any reasonably attainable inertial velocity (to use a term from E.E. Smith, who had the "free drive" aka "inertialess drive"), the thermal velocities of those particles will be several times that of the ship as a whole, and in literally random directions. Field powers up, and as soon as it reaches criticality, every particle is traveling at exactly lightspeed -- in whatever random direction it was before.

The field will collapse in nanoseconds, of course -- but by then, each electron etc. will be several feet from the atom it used to be part of. Unbalanced charges will then complete disassembly the entire vessel at the atomic scale, and the rebinding of electrons will emit a pulse of EM radiation comparable to a small nuclear explosion.

• @abestrange Exactly. – Zeiss Ikon Dec 10 '20 at 20:22
• Even a slight divergence would result in large discrepancies over interstellar distances. Your ship would also be susceptible to gravitational lensing that could spread out your "light rays" through even subtle gravitational gradients. – abestrange Dec 10 '20 at 20:26
• -1, mass is not required for chemical bonds. The atoms will not fly apart just because their mass is set to zero. – vsz Dec 11 '20 at 13:12
• @vsz Really? Even when the electrons are at lightspeed relative to the nucleus? And each nucleus (due to thermal velocities, even in a solid) the same relative to every other nucleus? You'll have what amounts to a cloud of plasma, expanding at the speed of light, for several nanoseconds while the field collapses. Every solid object will be spread out by a couple meters from its original size/shape. Chemical bonds will have to reform. – Zeiss Ikon Dec 11 '20 at 13:47
• I think @vsz has a point. Imagine you have a hydrogen atom (one electron, one proton) and then you magically make both of those particles massless. Well, you still need energy to remove the electron from the proton, and as far as I know, you haven't added any energy, so the electron can't escape. Even if it's moving at the speed of light, that doesn't mean it'll travel a significant distance in a straight line. – Tanner Swett Dec 11 '20 at 18:00

Physicist here. Yes, your zero mass field does pass the handwave test for me.

But.

If you are comfortable approaching the hard science line of science fiction, note that according to current theory, it is the Higgs field providing mass to particles. Why not call it the negative (or anti-) Higgs field? "Scotty, engage the Higgs Quench!", "Damage report: our Higgs Choke needs repair."

Next, zero mass particles travel at the speed of light. A direct consequence is that they don't experience the passage of time. There is no way they can intrinsically change. At all. So your zero mass space ship cannot, by principle, have a clock telling them when it's time to go to positive mass again. The cause must come from outside, i.e. something at the destination.

This would be much easier if you only went to near light speed: enter neutrinos! They are so light (no pun intended), the most gentle of nudges accelerates them to near light speed. And you'd completely eliminate one of the deadliest risks of high speed travel: running into space dust, or rocks, or planets, or stars. Even stars are all but transparent for the neutrino ship (please manoeuvre around Black holes, though.) And since time passes for neutrinos (they could not change type otherwise), you can carry a functioning clock aboard your ship to tell when it is time to become more massive again.

• Completely agree with this, going 99.999% of light speed is hugely preferable to going 100% light speed – Kevin Wells Dec 11 '20 at 18:18
• The people in the story can still colloquially call it ‘light speed’; then somebody makes an offhand comment that it's not quite light speed, but close enough for practical purposes (the trip is nearly instantaneous to the travellers, they arrive almost as quickly as you'd expect); then it's important to the plot that one ship's ‘light speed’ might actually be significantly faster than another's, even though most people don't think of this, so somebody can catch up with somebody else who thought that they got away; …. – Toby Bartels Dec 12 '20 at 23:59

I fully agree with The Square-Cube Law's answer that your concept is good enough for SciFi that does not aim to adhere particularly well to the physics we know.

Nevertheless, here are some problems physicists may have with your concept:

• As Zeiss Ikon noted in their answer, random particle movements will destroy your ship if the particles go light speed in the direction they have.

• However, what exactly is the direction of movement? Are we looking at it from the perspective of earth? Or the perspective of the sun? Or the perspective of our galaxy? From the perspective of which galaxy, btw?

You see, even special relativity says that there is no such thing as being at rest. You can only ever be at rest relative to something else, but you are are always moving in all sorts of direction, depending what you choose as your reference. And all these references are equally valid. As such, you cannot say: This ship switches to light speed in the direction it's currently moving.

• For the ship, and thus for the field generator, time stops completely. The ship simply cannot switch off the field generator. It simply crashes into whatever is the first thing on its line of movement. At light speed. Do I need to say that the explosion would make the Tzar Bomba a fire cracker in comparison? Larry Niven made this exact same mistake with his Slaver Stasis field in his ringworld novel. (He made some more mistakes, but never mind.)

• Energy and mass are equivalent, and the conservation of energy is the most fundamental rule in our universe. If you change the mass, you are changing the amount of energy, and physicists just won't buy this idea. They are quite particular about energy/mass conservation. Time and time again, whenever an experiment showed a discrepancy in energy, it led to the discovery of new physics, but the energy/mass conservation principle remained entirely untouched. Nothing of the weirdest physics we know today provides any indication that it might not hold in even the most extreme environment.

• Space is not empty. Your massless particles will encounter stuff on their way. The collision may turn any grain of dust into a plasma, but the plasma cannot get out of the way of the following massless particles. As such, each grain of dust you encounter will punch a hole right through your ship. I would hate to look like a microscopic piece of Swiss cheese after a lightspeed voyage. It won't be healthy.

I think, you best bet would be to say that the field generator is external to the ship, and that it sets the direction of travel. It basically converts the ship into its massless form. The destination is selected by setting up an anti field at the destination, which turns any incoming massless particles massive again. You could think of it like extreme distance beaming. I see no way of explaining the last point away, but I think that it would be safe to simply ignore this issue.

• If the field is moving through space along with the matter-converted-into-energy ship, then any space debris you ran into could also get converted to energy. How do you supply the energy to perform that work, and how do you deal with the huge amounts of gained energy from all the space-junk in your path, is an exercise left best to the reader. – abestrange Dec 10 '20 at 21:35
• "Energy and mass are equivalent, and the conservation of energy is the most fundamental rule in our universe. If you change the mass, you are changing the amount of energy, and physicists just won't buy this idea." – I don't think this objection is really so objectionable. It's completely possible for massive particles to be converted entirely into massless particles and back—for example, an electron and a positron can turn into a photon, which can turn back into an electron and a positron. The photon is described as being massless even though it still has energy. – Tanner Swett Dec 11 '20 at 19:37
• The proposal here is merely a more extreme version of the same thing. – Tanner Swett Dec 11 '20 at 19:38
• @TannerSwett 1. When you annihilate an electron/positron pair, you get a pair of photons. This is necessary for conserving momentum: In the reference frame of the center of mass the two particles collide head on with equal speed, and two photons are created, also with equal energy and momentum in opposite directions. 2. The energy of the photons is equal to the mass + kinetic energy of the electron/positron pair. And this energy of the photons bends space just like the massive particles did. No mass is removed, only converted. But yes, the mass/energy is now carried away at the speed of light. – cmaster - reinstate monica Dec 11 '20 at 19:53
• @TannerSwett it's probably better to think about energy-momentum 4-vector. The metric of it is conserved in all frame of reference and is rest mass. Therefore to change mass you need to change energy or momentum (or both). So there is a law of physics that you need to break (if it is good enough for handwaveium is another matter). – Maciej Piechotka Dec 12 '20 at 10:04

While you see zero mass fields often enough in Scifi to be believable to a general audience, the Higgs Mechanism pretty much disproves them as a possibility.

The Higgs Mechanism is the prevailing theory right now about where mass comes from. It explains that mass is a function of the interactions between fundamental particles. For Electrons, it is caused by drag with the Higgs Boson Field, and for Protons and Neutrons, it is mostly caused by the much stronger interactions between Quarks and Gluons. So to eliminate Mass you would need to eliminate all of the interactions between all of the fundamental particles in your spaceship. This means there would be no forces left to hold you together... at least until the field generator comes apart and all of your matter has to find a way to reassemble.

Best case scenario this will turn you into a sort of nuclear bomb. Worst case scenario, it will turn you into something much worse: a Quark Bomb. Quarks are bound together by the strong force which makes them really really hard to get apart, but if you eliminate the strong force for a while, all the quarks in your body will drift apart... but when your anti-mass field disappears, they will snap together with the strongest force known to man. Quark bombs are a lot of theory with only a tiny amount of observable data, but various models indicate that a quark explosion could be anywhere from 8 times as energetic as a same mass hydrogen bomb reaction to being even more powerful than a matter/anti-matter reaction.

So let's say you have a spaceship the size of the Enterprise-D, and put it into an anti-mass field. The resulting Quark explosion would be anywhere from about 6 to 107 billion megatons assuming you cap your explosion as a pure matter to energy conversion.

But as I said, a quark bomb might be even more powerful than antimatter. This may seem to violate the conservation of mass and energy, but the strong force becomes stronger as you move two bound quarks apart instead of weaker like electromagnetism or gravity. I don't know exactly how scientific this is, but some authors have taken this to mean that a single neutron can store infinite potential energy based on how far apart you pull its bound quarks. So, it is possible that your ship could even explode with all of the force of a supernova wiping out all life in the solar system.

So, zero mass fields make for GREAT weapons and possibly some very interesting power reactors, but not so much good as a form of propulsion as described.

Instead Use a Near Zero Mass Field

One of the problems with math & physics is that it tends to fall apart when you start working with zero or infinite values. So, instead of a zero mass field, what happens if you just reduce your mass? The attraction between your fundamental particles will become weaker, but so will their inertia so an atom with 1 millionth of its normal mass will only be held together by 1 millionth of its normal binding forces, but it is also 1 million times as easy to manipulate; so, it could still (in theory at least) hold its normal shape and form acting totally normal within your local physics system.

So lets say your ship is flying along at a humble 10 km/s, but you want to be moving at 0.9 c, you just reduce your mass to about .00000014% of normal. You are WAY less massive and have way less inertia, but still have a proportional amount of binding energy to inertia to maintain normal cohesion.

This might also help protect you from relativistic collision problems. Inside your own field you are still only experiencing forces comparable to moving at 10kps; so, even if you run into some space dust at 270,000 km/s, the dust will become part of your local physics system and the impact will feel like a 10 km/s impact: which you can much more easily armor you ship against.

Local physics fields of any sort are still pretty soft-science any way you add it up, but at least this should pass some basic believability checks as to why you don't just explode.

... and maybe use a Quark reactor to Power your Ship

If you have the ability to just turn on and off the fundamental forces of the universe, then depending on what model you go with, you may also have a virtually infinite power supply. Your ship could have a reactor that simply takes a tiny amount of regular matter, lets it drift apart far enough, and then slam back together releasing more energy than your fuel has mass. Since your ship can now violate the conservation of mass and energy, you could in theory accelerate your ship past the speed of light. Or if you go with a model that says a Quark explosion maxes out as a 1:1 mass to energy conversion, then you still have something as efficient as an antimatter reactor, but much easier to control and use for practical purposes.

• Another fun thing is that turning off the Higgs field would also reduce the masses of W and Z to zero, meaning weak interaction suddenly is not range limited. I wonder what would happen to the background of neutrinos in such an environment, if they suddenly start to feel each other's hypercharges. – Lars H Dec 11 '20 at 14:42
• Quark bombs! I love you 3,000 for introducing me to such a concept. I can see it now. My Elon Musk style character at mission headquarters is overseeing the launch of the prototype unmanned light speed drone to Mars. T-minus 3, 2, 1, BOOM! "Hawthorne, we have a problem." - Moon Base Thankfully, the launch was from Lagrange Point Waystation and all we get on Earth is a fantastic light show plus a telecommunications blackout. Sucks to be one of the inhabitants of the waystation, but their families will be well taken care of. – HyperNym Dec 13 '20 at 5:59
• @HyperNym If you are interested in adding quark bombs to your story, I should probably disclose that I undersold the true range of theories about how powerful quark bombs might be since some models seem to violate E=MC2 ... See revised answer. – Nosajimiki Dec 14 '20 at 15:03

Its a good question and other answers brought up some good points, so I'll focus on what mass is (and isn't).

The essence of the problem appears to breakdown to two fundamental questions:

Is it true that anything with mass can't reach the speed of light? (because to do so would require infinite energy.)

and

Do all massless particles HAVE to be moving at light speed?

If we render massive particles massless to go the speed of light and then return them to their massive state?

To get an understanding of the answer to these questions, we have to understand what mass is in the first place. Mass is quantity which describes the degree to which an interaction will change the energy of a particle. In a classical sense this is easy to understand, a force acts upon a mass, and the magnitude of mass directly (through inverse variation) determines how much energy that mass will gain. The energy gain is expressed as an increase in kinetic energy which is expressed through an increase in speed.

This classical picture is not enough to describe phenomena near the speed of light however. This is because the phenomena known as the (Relativistic) Dispersion relation which mathematically is expressed as $$E^2 = (p c)^2 + (m_o c^2)^2$$ and is invariant under space-time transformations. So in a classical sense we can think of a particle as "gaining" mass as its speed approaches that of the speed of light. This is because in the classical sense, for a force of F acting on a particle moving near the speed of light, the increase in kinetic energy will not be equal to the increase in kinetic energy from that same force at speeds well below the speed of light. For this reason we say that the particle gains "relativistic" mass. Since this relativistic mass is given by : $$\gamma m_o$$ where $$\gamma$$ is the Lorentz factor $$\frac{1}{\sqrt{1-(\frac{v}{c})^2}}$$, we note that a singularity occurs when v = c. In other words, at the speed of light, relativistic mass would be infinite, and therefore an infinite force would be required to provide infinite energy to achieve this speed. The answer to the first question would be a yes.

Now this is all well and good in the classical picture, but we have to consider the particles themselves. For example, this spaceship is composed of massive particles (electrons, neutrons and protons). A quantum picture view of mass is a little more complicated than the classical picture. This is because mass places more restrictions on the behavior of quantum particles than on classical particles. For example, massive particles can be described through wavefunctions. Wavefunctions describe "where" the particle is and how much energy the particle has and how that energy is tallied. If a particle is massless on the other hand, it cannot be described though a wavefunction, the best it can be described with is through a wave-packet. Without going into the mathematics of this, mass therefore fundamentally is connected with descriptions of localization and state.

This brings us to the second question. In special relativity, a massless particle must propagate at the speed of light; because the rest mass is zero and the dispersion relation must hold true, we conclude that massless particles must move at exactly the speed of light. In the quantum picture, because massless particles cannot be described as localized states, propagation in free-space does not violate the uncertainty principle: we can know a photon's energy (from its wavelength) in free-space because we cannot know where it is at (no localized states). For this reason photons (and presumably gluons) cannot interact in a vacuum as long as mass is not involved. Thus this means that the second question is also answered in the affirmative. However, this extra layer of restriction means that massive particles cannot become massless particles without destroying all information on their states (this processes is known as annihilation). Thus the third question is answered in the negative.

To conclude, current understanding of theoretical physics does not allow for massive particles to move at the speed of light, nor does it allow for massive particles to be converted to massless particles and then back again while retaining any information on the first states of the massive particles.

• There are a couple of mathematical mistakes here: the dispersion relation needs a square on $c$ in $m_oc$ (in addition to the square outside it, so $(m_oc^2)^2$); the Lorentz factor needs a square root. (I submitted an edit to fix these, but it's still awaiting approval.) – Toby Bartels Dec 13 '20 at 0:07
• @TobyBartels You are correct, the typos have been corrected. – user110866 Dec 13 '20 at 5:44

It might work, sort of (E. E. "Doc" Smith's Bergenholm inertialess drives did even better).

The problem lies in the interaction with the rest of the Universe: moving at the speed of light, you will perceive every idrogen ion in vacuum as a sleet of hard cosmic rays, and the ship's prow will start to photodisintegrate. The same would happen to the background radiation; that is why we shouldn't be able to detect protons with energy above a given range from other galaxies. The blueshifted-to-hard-gamma CMB gets them, and it would likely kill your ship too. You'd need a large beryllium-iron-lead shield in front to absorb the impact (it would be a good plot point, perhaps. Just like the ships of old, you'd need to stop every now and then for careening - removing the secondary radiation-activated plates from the hull, and replacing them with fresh ones).

Also, outer space is relatively full of dust - and, worse, pebbles. Hit one of those when traveling at c, and it's just as if someone had hit you with a gigawatt gamma laser. You'd need to carefully evaluate the route. Possibly, you'd need a sensor probe to run ahead of the ship, and come back to report before you follow the same route; this would imply that even the apparent speed of the ship would decrease significantly, while still remaining very high (one lightyear "jump" every minute?). "Running blind" would be faster if you knew with very, very good confidence a dust-free route.

Also, dispersing some thousand tons of metallic dust over a very large volume could be a way of stopping, and maybe destroying, a ship. In your universe, a stern chase would be a suicide chase.

There are many negative answers, and honestly I think that's a bit unfair. The main thing I want to say is yes, it does pass the handwave test. It makes far more scientific sense than warp drives or hyperdrives or most versions of wormholes. If we're not in the world of hard science I'd say this is definitely in the upper quartile of vaguely believable interstellar travel in science fiction.

If you want to set the bar a bit higher for scientific accuracy then there are certainly ways to nit-pick. The first, which some have mentioned, is that it doesn't make sense to say it keeps moving in the same direction unless you specify an inertial reference frame. (That is, it moves in the same direction relative to what?) But that's easily handwaved, either by saying there's some kind of pervasive field that it moves relative to, or by saying that the drive behaves like a photon emitter, turning the ship into a massless particle travelling in a particular pre-specified direction. Perhaps it emits a single massive particle in the opposite direction, which is all it needs to in order to achieve that.

The other potential nitpick is energy conservation. If you could Zero Mass your way out of a planet's gravitational well and then fall back in again, you'll have gained kinetic energy for free. That would break thermodynamics, so if you want to be realistic you'd have to make sure that's not possible. But this actually suggests an answer to the "how do you stop?" question: the ship turns back into normal matter if and when it has exactly the same kinetic and potential energy it had when it turned massless. To travel from one planet to another you have to set your trajectory very precisely so that you'll pass through the other planet's gravity well. Then (from your perspective) you'll jump straight from being in orbit around one planet to being in orbit around the other, so you never gained any gravitational potential. (Of course, space is very big and very empty, so if you miss you'll most likely end up travelling through space until the heat death of the universe, and then keep going for all eternity - none of which you'll experience due to the time dilation. So don't miss.)

One could probably nitpick all of the above also, but I guess that's not the point. The main point is that if you're not going for absolute physical realism then I think it's fine, and you shouldn't let some of the other answers convince you otherwise.

The idea checks out at first.

My biggest problem is that you don't talk about what the field does and how. You just say "everything in the field has zero mass", which like no.

The problem is that mass is just a form of energy and saying the mass is zero thus is equal to saying the energy is zero. Which implies that nothing is in the field. So your current field is more like a "Energy Annihilation Field" which tbh is pretty cool.

Your field would make more sense if you say it for example "converts all energy forms into a massless equivalent". That would imply that matter becomes some form of energy that has no mass. The energy is not zero, it is still there just in a different form.

So yeah, change how you describe it and we are gucci.

• I think OP meant "zero rest mass", not "zero relativistic mass". – Ruther Rendommeleigh Dec 11 '20 at 9:43

How about using something to locally disrupt the Higgs field? The Higgs field gives mass to particles (not entirely true, but handwaving can make it so), so it is plausible enough that somehow shielding against it makes things mass-less. The Higgs boson is the latest great thing, so ought to be persuasive.

• So... Cavorite, but with a projected bubble rather than plating? – Ruadhan Dec 11 '20 at 15:03
• Antigrav bubbles, cancelling their contents' gravity signature sound like an evolution of stealth tech, preceding the well-known hover tech seen in Star Wars and making Alcubierre warp drives more feasible. – Cees Timmerman Dec 13 '20 at 12:09

Let me suggest an alternative. There is a preferred rest frame but it just appears as if there isn't simply because the normal time dilation/length compression effects prevent us from noticing them (as the math requires) but you can raise that speed in a small volume. In other words the model here is that of a world with an infinite speed of light but with a background ether which slows it down to c (just like any dielectric) which normal physics can't detect because it's perfectly hidden by the math (you can derive SR just from assumption that all matter is in an equilibrium under inverse square laws with force carriers traveling at light speed…as it must for SR to be consistent) Now you just add some kind of effect which lets you push the either out of a nearby volume of space returning c to infinity

This has a kinda interesting fun side-effect. If you apply this field to an object that's already moving very fast relative to the true rest-frame you get a huge release of energy that vaporizes that object. It's as if the object was squashed by the length contraction factor and then suddenly allowed to expand to its equilibrium state. Of course this model is totally classical but it is actually consistent though it has some issues in details (classical decay of electron orbits).